Reactive Programming

Introduction to Reactive Programming

Transcript

1. Reactive Programming
2. What is Rx?
3. • “Reactive programming” is a general term about programming focused on reacting to changes, such as data values or events. • Acting in response to a situation rather than creating or controlling it. • async** resonsive ui
4. Why going reactive?
5. • When working with results set It is better to start processing individual result when they are ready • World has moved to push technology • Asynchronous programming is very important
6. Imperative vs declarative programming
7. • declarative tells what to do • imperative explains how to do
8. final List<BigDecimal> prices = getPriceList() Calculate the total price greater than $20, discounted by 10%
9. Imperative approach
10. Declarative approach
11. Reactive programming in Java
12. • Java 8 Stream api • Reactive extension for Java by Netflix
13. RxJava
14. • JVM implementation of ReactiveX • Ported by Netflix • Seems like just a library but it’s also the new paradigm of programming
15. • JVM implementation of ReactiveX • Ported by Netflix • Seems like just a library but it’s also the new paradigm of programming
16. Observer pattern on Steroid
17. Observer Pattern
18. Observer Pattern • Observable for Subject • Observer is same
19. • JVM implementation of ReactiveX • Ported by Netflix • Seems like just a library but it’s also the new paradigm of programming
20. Reactive Manifesto
22. Responsive A responsive system is quick to react to all users  — under blue skies and grey skies — in order to ensure a consistently positive user experience.
23. Resilient A resilient system applies proper design and architecture principles in order to ensure responsiveness under grey skies as well as blue.
24. Event Driven A message-driven architecture is the foundation of Reactive applications. A message-driven application may be event-driven, actor-based, or a combination of the two.
25. Scalable A scalable system is easily upgraded on demand in order to ensure responsiveness under various load conditions.
26. Building Blocks of RxJava
27. • Observable (producer) • Observer (consumer) • Subscription (connection)
28. Observable
30. Stream Observable represents a stream of data or events.
31. • Emits zero or more items • then it terminates either by successfully completing, or due to an error.
32. Types of Observable: 1. Hot : begins emitting as soon as created (e.g. stream of mouse click) 2. Cold : waits until an observer subscribes it (e.g. Network request)
33. Observer
34. • Observer are the consumer of the data • Observer listens to Observable • Subscriber is special observer that can unsubscribe from data source
35. Subscription
36. • Used to unregister Subscriber from Observable • Release the resources.
37. How RxJava Works
39. • The Observable represents the stream of data and can be subscribed to by an Observer. • Events are pushed to observer
40. Upon subscription, the Observer can have 3 types of events pushed to it: 1. data via the onNext function 2. errors (Exceptions or Throwables) via the onError function 3. stream completion via the onCompleted function
41. Rxjava is sync until told Asynchrony
42. Schedulers: Asynchrony
43. Schedulers provide concurrency for observables Asynchrony
44. Perform work on specific scheduler Observable.observeOn(Scheduler s) Observe the result on given scheduler Observable.subscribeOn(Scheduler s) Asynchrony
45. cod e
46. Observable Creation
47. Creating Observable
48. Creating Observable • For converting single object Observable.just() • For converting list or arrays of object Observable.from() • Design your own observable Observable.create()
49. Operators
50. Map
51. Flat Map
52. FlatMap List<Developer> developers = getDevelopers(); List<String> teamLanguages = Observable.from(developers). map(d -> d.getLanguages()). flatMap(l -> l.stream()). toList(); public class Developer { private String name; private List<String> languages; public List<String> getLanguages() { return this.languages; } }
53. Filter
54. take
55. Merge
56. Zip
57. Zip
58. /photo, /metadata Observable.zip( service.getUserPhoto(id), service.getPhotoMetadata(id), (photo, metadata) -> createPhotoWithData(photo, metadata)) .subscribe(photoWithData -> showPhoto(photoWithData)); Zip
59. Debounce
60. Chaining Async Network Requests
61. Chaining
62. Search
63. Questions??